Tcl

Tcl (Tool Command Language, often said “tickle”) was created by John Ousterhout at UC Berkeley in 1988 as a small language to embed in other programs. With its Tk toolkit it became a quick way to build desktop interfaces, and it still runs inside chip-design tools, network test equipment, and Expect, the classic tool for scripting interactive programs.

Tcl has almost no syntax. Every line is a command followed by its arguments, and every value is a string. $name substitutes a variable, [command] runs a command and substitutes its result, and {braces} quote text without substituting anything. Even if and while are ordinary commands that take their bodies as braced strings. Arithmetic happens only inside expr. Lists and dictionaries are built in; Tcllib, the large add-on library with statistics and matrix packages, isn’t installed here.

Quirks

• lsort compares text unless told otherwise, so lsort {3.5 1.25 2 10} gives 1.25 10 2 3.5. lsort -real sorts them as numbers.
• Brace your expressions. With set x "1 + 2", expr $x gives 3, because Tcl substitutes $x first and expr then reads the text as code. expr {$x} gives back the string 1 + 2.
• 7 / 2 is 3, and -7 / 2 is −4: integer division rounds down, not toward zero. 7 / 2.0 is 3.5.
• foreach x {1 2 3} y {a b} walks both lists in step, and when one runs out, it pads with empty strings instead of stopping: the last pass gets x = 3 and an empty y.
• Integers never overflow: 2**70 is 1180591620717411303424.
• == compares numbers when it can: "10" == "10.0" is true, while string equal 10 10.0 is false.

git clone https://github.com/qnixon/dswithx.git
cd dswithx
python3 harness/run_tests.py --language tcl