September 2017 Update

Task/URL-decoding/Jq/url-decoding-1.jq

@@ -0,0 +1,27 @@
+# Emit . and stop as soon as "condition" is true.
+def until(condition; next):
+  def u: if condition then . else (next|u) end;
+  u;
+
+def url_decode:
+  # The helper function converts the input string written in the given
+  # "base" to an integer
+  def to_i(base):
+    explode
+    | reverse
+    | map(if 65 <= . and . <= 90 then . + 32  else . end)   # downcase
+    | map(if . > 96  then . - 87 else . - 48 end)  # "a" ~ 97 => 10 ~ 87
+    | reduce .[] as $c
+        # base: [power, ans]
+        ([1,0]; (.[0] * base) as $b | [$b, .[1] + (.[0] * $c)]) | .[1];
+
+  .  as $in
+  | length as $length
+  | [0, ""]  # i, answer
+  | until ( .[0] >= $length;
+      .[0] as $i
+      |  if $in[$i:$i+1] == "%"
+         then [ $i + 3, .[1] + ([$in[$i+1:$i+3] | to_i(16)] | implode) ]
+         else [ $i + 1, .[1] + $in[$i:$i+1] ]
+         end)
+  | .[1];  # answer

Task/URL-decoding/Jq/url-decoding-2.jq

@@ -0,0 +1 @@
+"http%3A%2F%2Ffoo%20bar%2F" |  url_decode

Task/URL-decoding/Jq/url-decoding-3.jq

@@ -0,0 +1 @@
+"http://foo bar/"