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10.4.5  Using strings as commands

The expr command will let you use a string as a command. Given a string that expresses a valid command, expr will convert the string to the command and evaluate it. For example, if you enter

expr("c := 1")

then the variable c will be set to 1. Similarly, if you enter

a := "ifactor(54)"



will return

2 * 3^3

which is the same thing as entering ifactor(54) directly.

You can also use expr to convert a string to a number. If a string is simply a number enclosed by quotation marks, then expr will return the number. For example,


will return


In particular, the following strings will be converted to the appropriate number.

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