Tutorial: variables, assignment

1.1.4 Tutorial: variables, assignment

CoCoA-5 includes its own imperative programming language. Values you plan to use in future computations need to be stored in variables; the act of storing a value in a variable is also called assignment. CoCoA-5 uses the colon-equals operator to indicate assignment, for instance A := 13; assigns 13 to the variable A.

A variable name must start with a letter, and may contain letters, digits, and the underscore character. We recommend using names which are mnemonic (but hopefully not too long).

The most basic types in CoCoA-5 are integers, rationals and strings. A number written in "decimal notation" is automatically converted to a rational number: for example 3.14 is converted into the fraction 157/50.

Example

/**/ A := 1;          // assign the integer 1 to the variable "A"
/**/ half := 1/2;     // assign rational 1/2 to the variable "half"
/**/ A := 0.333;      // assign the rational 333/1000 to "A"
                      // The previously stored value is overwritten.
/**/ mesg1 := "hi!";  // assign the string "hi!" to variable "mesg1"