Convert inputs of join to strings

README.md

@@ -569,10 +569,11 @@ The interpretation of `reduce`/`foreach` in jaq has the following advantages ove
   When there is no more input value left,
   in jq, `input` yields an error, whereas in jaq, it yields no output value.
 * Joining:
-  When given an array `[x0, x1, ..., xn]`,
-  in jq, `join(x)` converts all elements of the input array to strings and intersperses them with `x`, whereas
-  in jaq, `join(x)` simply calculates `x0 + x + x1 + x + ... + xn`.
-  When all elements of the input array and `x` are strings, jq and jaq yield the same output.
+  When giving an array `[x1, ..., xn]` to `join($sep)`, jaq returns
+  `""` if the array is empty, otherwise `"\(x1)" + $sep + ... + $sep + "\(xn)"`;
+  that is, it concatenates the string representations of the array values interspersed with `$sep`.
+  Unlike jq, jaq does not map `null` values in the array to `""`,
+  nor does it reject array or object values in the array.
 
 
 

jaq-std/src/defs.jq

@@ -84,7 +84,7 @@ def map(f): [.[] | f];
 def map_values(f): .[] |= f;
 def add(f): reduce f as $x (null; . + $x);
 def add: add(.[]);
-def join(x): .[:-1][] += x | add;
+def join($x): .[] |= tostring | .[:-1][] += $x | add + "";
 def min_by(f): reduce min_by_or_empty(f) as $x (null; $x);
 def max_by(f): reduce max_by_or_empty(f) as $x (null; $x);
 def min: min_by(.);

jaq-std/tests/defs.rs

@@ -76,14 +76,13 @@ yields!(
     false
 );
 
-yields!(join_empty, r#"[] | join(" ")"#, json!(null));
+yields!(join_empty, r#"[] | join(" ")"#, "");
 yields!(
     join_strs,
     r#"["Hello", "world"] | join(" ")"#,
     "Hello world"
 );
-// 2 + 1 + 3 + 1 + 4 + 1 + 5
-yields!(join_nums, r#"[2, 3, 4, 5] | join(1)"#, 17);
+yields!(join_nums, r#"[2, 3, 4, 5] | join(",")"#, "2,3,4,5");
 
 yields!(map, "[1, 2] | map(.+1)", [2, 3]);