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COS 320 Class Notes

# COS 320 Class Notes - val d bool = true d is declared and...

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COS 320 Class Notes Feb 3 rd Main Course Webpage: moodle.cs.princeton.edu/course/view.php?id=42 Programming in ML: - ML is a language developed in the 1970’s, designed as a “controlling theorem prover.” - To run in Windows, use EMACS. - To run ML: \$ sml.bat - ML is interactive – commands are executed on-the-fly, not in a file. (Although you can prep a file and execute from the file if you wish.) To run files as programs: - use “01.sml” where “01.sml” is the filename, “-“ is the prompt, and “use” is the ML command NOTE: Using commands -- the “use” command is “string unit” (meaning it takes a string and returns a unit.) Conventions of the language: - val d = true; d is declared and implied to be a Boolean from the expression
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Unformatted text preview: - val d : bool = true; d is declared and specified to be a Boolean!- val a = 11;- val a = 12; a is declared as “11” and then redeclared as “12.” In ML, the “redeclaring” is called “hiding” the old value… the old a is still kept in memory, but inaccessible.- val x = ref 0; x is a reference (a pointer) to a block in memory which stores “0”- x := 7; changes the value in memory from “0” to “7”- !x; returns value pointed to by x; right now, is “7” value it = syntax for returning an answer where the input variable is not specified ? value it = use(“___”) A way to run a file as a program (?)...
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