fix: Correct division precedence without paretheses everywhere

Follow up to PRQL#3969.

I think this is a pretty reasonable fix. There are probably some instances where it has too many parentheses, but very few. And it uses our existing approach, doesn't require any big changes.

prqlc/prql-compiler/src/sql/std.sql.prql

@@ -125,14 +125,19 @@ let read_csv = source -> s"read_csv({source:0})"
 let mul = l r -> null
 
 @{binding_strength=100}
-let div_i = l r -> s"FLOOR(ABS({l:11} / {r:11})) * SIGN({l:0}) * SIGN({r:0})"
-
-# We have a simple float division by default, but it can be overridden by dialects.
+let div_i = l r -> s"FLOOR(ABS({l:11} / {r:12})) * SIGN({l:0}) * SIGN({r:0})"
+
+# We have a simple float division by default, but it can be overridden by
+# dialects.
+# Note that this uses `12` for the RHS binding strength, which is one more than
+# binding strength of divison. That's because we don't use associativity here,
+# and so we need to make sure that the RHS is parenthesized when the binding
+# strengths are equal; e.g. in `a / (b / c)`.
 @{binding_strength=11}
-let div_f = l r -> s"{l} / ({r})"
+let div_f = l r -> s"{l} / {r:12}"
 
 @{binding_strength=11}
-let mod = l r -> s"{l} % ({r})"
+let mod = l r -> s"{l} % {r:12}"
 
 @{binding_strength=10}
 let add = l r -> null
@@ -176,12 +181,12 @@ let not = l -> s"NOT {l}"
 
 module ansi {
   @{binding_strength=11}
-  let div_f = l r -> s"({l} * 1.0 / ({r}))"
+  let div_f = l r -> s"({l} * 1.0 / {r:12})"
 }
 
 module bigquery {
   @{binding_strength=11}
-  let div_f = l r -> s"({l} * 1.0 / ({r}))"
+  let div_f = l r -> s"({l} * 1.0 / {r:12})"
 
   # Mathematical functions
   module math {
@@ -196,10 +201,10 @@ module bigquery {
 module clickhouse {
   # https://clickhouse.com/docs/en/sql-reference/functions/arithmetic-functions#divide
   @{binding_strength=11}
-  let div_f = l r -> s"({l} / ({r}))"
+  let div_f = l r -> s"({l} / {r:12})"
 
   @{binding_strength=11}
-  let div_i = l r -> s"({l} DIV {r})"
+  let div_i = l r -> s"({l} DIV {r:12})"
 
   let regex_search = text pattern -> s"match({text:0}, {pattern:0})"
 
@@ -210,10 +215,10 @@ module clickhouse {
 
 module duckdb {
   @{binding_strength=11}
-  let div_f = l r -> s"({l} / ({r}))"
+  let div_f = l r -> s"({l} / {r:12})"
 
   @{binding_strength=11}
-  let div_i = l r -> s"TRUNC({l:11} / {r:11})"
+  let div_i = l r -> s"TRUNC({l:11} / {r:12})"
 
   # String functions
   module string {
@@ -234,7 +239,7 @@ module duckdb {
 
 module mssql {
   @{binding_strength=11}
-  let div_f = l r -> s"({l} * 1.0 / ({r}))"
+  let div_f = l r -> s"({l} * 1.0 / {r:12})"
 
   # Mathematical functions
   module math {
@@ -255,10 +260,10 @@ module mssql {
 
 module mysql {
   @{binding_strength=11}
-  let div_f = l r -> s"({l} / ({r}))"
+  let div_f = l r -> s"({l} / {r:12})"
 
   @{binding_strength=11}
-  let div_i = l r -> s"({l} DIV ({r}))"
+  let div_i = l r -> s"({l} DIV {r:12})"
 
   @{binding_strength=100}
   let mod = l r -> s"ROUND(MOD({l:0}, {r:0}))"
@@ -269,10 +274,10 @@ module mysql {
 
 module postgres {
   @{binding_strength=11}
-  let div_f = l r -> s"({l} * 1.0 / ({r}))"
+  let div_f = l r -> s"({l} * 1.0 / {r:12})"
 
   @{binding_strength=100}
-  let div_i = l r -> s"TRUNC({l:11} / ({r:11}))"
+  let div_i = l r -> s"TRUNC({l:11} / {r:12})"
 
   # Mathematical functions
   module math {
@@ -293,10 +298,10 @@ module postgres {
 
 module glaredb {
   @{binding_strength=11}
-  let div_f = l r -> s"({l} * 1.0 / ({r}))"
+  let div_f = l r -> s"({l} * 1.0 / {r:12})"
 
   @{binding_strength=100}
-  let div_i = l r -> s"TRUNC({l:11} / ({r:11}))"
+  let div_i = l r -> s"TRUNC({l:11} / {r:12})"
 
   # Mathematical functions
   module math {
@@ -324,10 +329,10 @@ module sqlite {
   let concat_array = column -> s"GROUP_CONCAT({column:0}, '')"
 
   @{binding_strength=11}
-  let div_f = l r -> s"({l} * 1.0 / ({r}))"
+  let div_f = l r -> s"({l} * 1.0 / {r:12})"
 
   @{binding_strength=100}
-  let div_i = l r -> s"ROUND(ABS({l:11} / {r:11}) - 0.5) * SIGN({l:0}) * SIGN({r:0})"
+  let div_i = l r -> s"ROUND(ABS({l:11} / {r:12}) - 0.5) * SIGN({l:0}) * SIGN({r:0})"
 
   # String functions
   module string {
@@ -345,5 +350,5 @@ module sqlite {
 module snowflake {
   # https://docs.snowflake.com/en/sql-reference/operators-arithmetic#division
   @{binding_strength=11}
-  let div_f = l r -> s"({l} / ({r}))"
+  let div_f = l r -> s"({l} / {r:12})"
 }

prqlc/prql-compiler/tests/integration/snapshots/integration__queries__compile__arithmetic.snap

@@ -37,32 +37,32 @@ WITH table_0 AS (
 )
 SELECT
   id,
-  x_int / (k_int),
-  x_int / (k_float),
-  x_float / (k_int),
-  x_float / (k_float),
+  x_int / k_int,
+  x_int / k_float,
+  x_float / k_int,
+  x_float / k_float,
   FLOOR(ABS(x_int / k_int)) * SIGN(x_int) * SIGN(k_int) AS q_ii,
   FLOOR(ABS(x_int / k_float)) * SIGN(x_int) * SIGN(k_float) AS q_if,
   FLOOR(ABS(x_float / k_int)) * SIGN(x_float) * SIGN(k_int) AS q_fi,
   FLOOR(ABS(x_float / k_float)) * SIGN(x_float) * SIGN(k_float) AS q_ff,
-  x_int % (k_int) AS r_ii,
-  x_int % (k_float) AS r_if,
-  x_float % (k_int) AS r_fi,
-  x_float % (k_float) AS r_ff,
+  x_int % k_int AS r_ii,
+  x_int % k_float AS r_if,
+  x_float % k_int AS r_fi,
+  x_float % k_float AS r_ff,
   ROUND(
-    FLOOR(ABS(x_int / k_int)) * SIGN(x_int) * SIGN(k_int) * k_int + x_int % (k_int),
+    FLOOR(ABS(x_int / k_int)) * SIGN(x_int) * SIGN(k_int) * k_int + x_int % k_int,
     0
   ),
   ROUND(
-    FLOOR(ABS(x_int / k_float)) * SIGN(x_int) * SIGN(k_float) * k_float + x_int % (k_float),
+    FLOOR(ABS(x_int / k_float)) * SIGN(x_int) * SIGN(k_float) * k_float + x_int % k_float,
     0
   ),
   ROUND(
-    FLOOR(ABS(x_float / k_int)) * SIGN(x_float) * SIGN(k_int) * k_int + x_float % (k_int),
+    FLOOR(ABS(x_float / k_int)) * SIGN(x_float) * SIGN(k_int) * k_int + x_float % k_int,
     0
   ),
   ROUND(
-    FLOOR(ABS(x_float / k_float)) * SIGN(x_float) * SIGN(k_float) * k_float + x_float % (k_float),
+    FLOOR(ABS(x_float / k_float)) * SIGN(x_float) * SIGN(k_float) * k_float + x_float % k_float,
     0
   )
 FROM

prqlc/prql-compiler/tests/integration/snapshots/integration__queries__compile__pipelines.snap

@@ -12,7 +12,7 @@ WITH table_0 AS (
     tracks
   WHERE
     REGEXP(name, 'Love')
-    AND milliseconds / (1000) / (60) BETWEEN 3 AND 4
+    AND milliseconds / 1000 / 60 BETWEEN 3 AND 4
   ORDER BY
     track_id
   LIMIT

prqlc/prql-compiler/tests/integration/sql.rs

@@ -247,18 +247,24 @@ fn json_of_test() {
 }
 
 #[test]
-fn test_precedence_again() {
+fn test_precedence_division() {
     assert_display_snapshot!((compile(r###"
     from artists
     derive {
-      p2 = x / (y * z), # needs parentheses
       p1 = a - (b + c), # needs parentheses
+      p2 = x / (y * z), # needs parentheses
+      np1 = x / y / z, # doesn't need parentheses
+      p3 = x / (y / z), # needs parentheses
+      np4 = (x / y) / z, # doesn't need parentheses
     }
     "###).unwrap()), @r###"
     SELECT
       *,
+      a - (b + c) AS p1,
       x / (y * z) AS p2,
-      a - (b + c) AS p1
+      x / y / z AS np1,
+      x / (y / z) AS p3,
+      x / y / z AS np4
     FROM
       artists
     "###);
@@ -295,8 +301,8 @@ fn test_precedence() {
     "###).unwrap()), @r###"
     SELECT
       *,
-      (temp_f - 32) / (1.8) AS temp_c,
-      (temp_f - 32) / (1.8) * 9 / (5) AS temp_f,
+      (temp_f - 32) / 1.8 AS temp_c,
+      (temp_f - 32) / 1.8 * 9 / 5 AS temp_f,
       temp_x + 9 - 5 AS temp_z
     FROM
       x
@@ -2986,7 +2992,7 @@ fn test_casting() {
       CAST(a AS int) + 10 AS b,
       CAST(a AS int) - 10 AS c,
       CAST(a AS float) * 10 AS d,
-      CAST(a AS float) / (10) AS e
+      CAST(a AS float) / 10 AS e
     FROM
       x
     "###

web/book/tests/documentation/snapshots/documentation__book__reference__declarations__functions__0.snap

@@ -4,7 +4,7 @@ expression: "let fahrenheit_to_celsius = temp -> (temp - 32) / 1.8\n\nfrom citie
 ---
 SELECT
   *,
-  (temp_f - 32) / (1.8) AS temp_c
+  (temp_f - 32) / 1.8 AS temp_c
 FROM
   cities
 

web/book/tests/documentation/snapshots/documentation__book__reference__declarations__functions__1.snap

@@ -4,8 +4,8 @@ expression: "let interp = low:0 high x -> (x - low) / (high - low)\n\nfrom stude
 ---
 SELECT
   *,
-  (sat_score - 0) / ((1600 - 0)) AS sat_proportion_1,
-  (sat_score - 0) / ((1600 - 0)) AS sat_proportion_2
+  (sat_score - 0) / (1600 - 0) AS sat_proportion_1,
+  (sat_score - 0) / (1600 - 0) AS sat_proportion_2
 FROM
   students
 

web/book/tests/documentation/snapshots/documentation__book__reference__declarations__functions__late-binding__0.snap

@@ -7,9 +7,9 @@ SELECT
   labor,
   overhead,
   cost_total,
-  materials / (cost_total) AS materials_share,
-  labor / (cost_total) AS labor_share,
-  overhead / (cost_total) AS overhead_share
+  materials / cost_total AS materials_share,
+  labor / cost_total AS labor_share,
+  overhead / cost_total AS overhead_share
 FROM
   costs
 

web/book/tests/documentation/snapshots/documentation__book__reference__declarations__functions__piping-values-into-functions__0.snap

@@ -4,8 +4,8 @@ expression: "let interp = low:0 high x -> (x - low) / (high - low)\n\nfrom stude
 ---
 SELECT
   *,
-  (sat_score - 0) / ((1600 - 0)) AS sat_proportion_1,
-  (sat_score - 0) / ((1600 - 0)) AS sat_proportion_2
+  (sat_score - 0) / (1600 - 0) AS sat_proportion_1,
+  (sat_score - 0) / (1600 - 0) AS sat_proportion_2
 FROM
   students
 

web/book/tests/documentation/snapshots/documentation__book__reference__declarations__functions__piping-values-into-functions__1.snap

@@ -4,7 +4,7 @@ expression: "let fahrenheit_to_celsius = temp -> (temp - 32) / 1.8\n\nfrom citie
 ---
 SELECT
   *,
-  (temp_f - 32) / (1.8) AS temp_c
+  (temp_f - 32) / 1.8 AS temp_c
 FROM
   cities
 

web/book/tests/documentation/snapshots/documentation__book__reference__declarations__functions__piping-values-into-functions__2.snap

@@ -4,7 +4,7 @@ expression: "let fahrenheit_to_celsius = temp -> (temp - 32) / 1.8\nlet interp =
 ---
 SELECT
   *,
-  ((temp_c - 32) / (1.8) - 0) / ((100 - 0)) AS boiling_proportion
+  ((temp_c - 32) / 1.8 - 0) / (100 - 0) AS boiling_proportion
 FROM
   kettles
 

web/book/tests/documentation/snapshots/documentation__book__reference__stdlib__README__standard-library__1.snap

@@ -8,7 +8,7 @@ WITH table_0 AS (
     5 AS y
 )
 SELECT
-  (x * 1.0 / (y)) AS quotient,
+  (x * 1.0 / y) AS quotient,
   ROUND(ABS(x / y) - 0.5) * SIGN(x) * SIGN(y) AS int_quotient
 FROM
   table_0

web/book/tests/documentation/snapshots/documentation__book__reference__stdlib__README__standard-library__2.snap

@@ -8,8 +8,8 @@ WITH table_0 AS (
     5 AS y
 )
 SELECT
-  (x / (y)) AS quotient,
-  (x DIV (y)) AS int_quotient
+  (x / y) AS quotient,
+  (x DIV y) AS int_quotient
 FROM
   table_0
 

web/book/tests/documentation/snapshots/documentation__book__reference__syntax__operators__division-and-integer-division__0.snap

@@ -13,7 +13,7 @@ WITH table_0 AS (
     -2 AS b
 )
 SELECT
-  (a * 1.0 / (b)) AS div_out,
+  (a * 1.0 / b) AS div_out,
   ROUND(ABS(a / b) - 0.5) * SIGN(a) * SIGN(b) AS int_div_out
 FROM
   table_0

web/book/tests/documentation/snapshots/documentation__book__reference__syntax__operators__parentheses__0.snap

@@ -7,7 +7,7 @@ SELECT
   distance BETWEEN 0 AND 20 AS is_proximate,
   SUM(distance) OVER () AS total_distance,
   MIN(COALESCE(distance, 5)) OVER () AS min_capped_distance,
-  distance / (40) AS travel_time,
+  distance / 40 AS travel_time,
   ROUND(distance, 1 + 1) AS distance_rounded_2_dp,
   distance >= 100 AS is_far,
   distance BETWEEN -100 AND 0,

web/book/tests/documentation/snapshots/documentation__book__reference__syntax__operators__wrapping-lines__1.snap

@@ -1,11 +1,11 @@
 ---
 source: web/book/tests/documentation/book.rs
-expression: "from tracks\n# This would be a really long line without being able to split it:\nselect listening_time_years = (spotify_plays + apple_music_plays + pandora_plays)\n# We can toggle between lines when developing:\n# \\ * length_seconds\n\\ * length_s\n#   min  hour day  year\n\\ / 60 / 60 / 24 / 365\n"
+expression: "from tracks\n# This would be a really long line without being able to split it:\nselect listening_time_years = (spotify_plays + apple_music_plays + pandora_plays)\n# * length_seconds\n# Actually it's `length_s` I think:\n\\ * length_s\n#   min  hour day  year\n\\ / 60 / 60 / 24 / 365\n"
 ---
 SELECT
   (
     spotify_plays + apple_music_plays + pandora_plays
-  ) * length_s / (60) / (60) / (24) / (365) AS listening_time_years
+  ) * length_s / 60 / 60 / 24 / 365 AS listening_time_years
 FROM
   tracks
 

web/website/data/examples/expressions.yaml

@@ -11,8 +11,8 @@ sql: |
   SELECT
     *,
     started + unfinished AS finished,
-    (started + unfinished) / (started) AS fin_share,
-    (started + unfinished) / (started) / ((1 - (started + unfinished) / (started)))
+    (started + unfinished) / started AS fin_share,
+    (started + unfinished) / started / (1 - (started + unfinished) / started)
      AS fin_ratio
   FROM
     track_plays

web/website/data/examples/functions.yaml

@@ -6,6 +6,6 @@ prql: |
   select temp_f = (fahrenheit_from_celsius temp_c)
 sql: |
   SELECT
-    temp_c * 9 / (5) + 32 AS temp_f
+    temp_c * 9 / 5 + 32 AS temp_f
   FROM
     weather