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8.2 Program flow commands

Below I show commands to control program flow, like, conditions, loops, define script arguments and so on. Other commands can be found in chapters MathGL core and Data processing. Note, that some of program flow commands (like define, ask, call, for, func) should be placed alone in the string.

MGL command: chdir 'path'

Changes the current directory to path.

MGL command: ask $N 'question'

Sets N-th script argument to answer which give the user on the question. Usually this show dialog with question where user can enter some text as answer. Here N is digit (0...9) or alpha (a...z).

MGL command: define $N smth

Sets N-th script argument to smth. Note, that smth is used as is (with ‘'’ symbols if present). Here N is digit (0...9) or alpha (a...z).

MGL command: define name smth

Create scalar variable name which have the numeric value of smth. Later you can use this variable as usual number.

MGL command: defchr $N smth

Sets N-th script argument to character with value evaluated from smth. Here N is digit (0...9) or alpha (a...z).

MGL command: defnum $N smth

Sets N-th script argument to number with value evaluated from smth. Here N is digit (0...9) or alpha (a...z).

MGL command: call 'funcname' [ARG1 ARG2 ... ARG9]

Executes function fname (or script if function is not found). Optional arguments will be passed to functions. See also func.

MGL command: func 'funcname' [narg=0]

Define the function fname and number of required arguments. The arguments will be placed in script parameters $1, $2, ... $9. Note, script execution is stopped at func keyword, similarly to stop command. See also return.

MGL command: return

Return from the function. See also func.

MGL command: load 'filename'

Load additional MGL command from external module (DLL or .so), located in file filename. This module have to contain array with name mgl_cmd_extra of type mglCommand, which describe provided commands.

MGL command: if dat 'cond'

Starts block which will be executed if dat satisfy to cond.

MGL command: if val

Starts block which will be executed if val is nonzero.

MGL command: elseif dat 'cond'

Starts block which will be executed if previous if or elseif is false and dat satisfy to cond.

MGL command: elseif val

Starts block which will be executed if previous if or elseif is false and val is nonzero.

MGL command: else

Starts block which will be executed if previous if or elseif is false.

MGL command: endif

Finishes if/elseif/else block.

MGL command: for $N v1 v2 [dv=1]

Starts cycle with $N-th argument changing from v1 to v2 with the step dv. Here N is digit (0...9) or alpha (a...z).

MGL command: for $N dat

Starts cycle with $N-th argument changing for dat values. Here N is digit (0...9) or alpha (a...z).

MGL command: next

Finishes for cycle.

MGL command: once val

The code between once on and once off will be executed only once. Useful for large data manipulation in programs like UDAV.

MGL command: stop

Terminate execution.

MGL command: variant val

Set variant of argument(s) separated by ‘?’ symbol to be used in further commands.

MGL command: rkstep eq1;... var1;... [dt=1]

Make one step for ordinary differential equation(s) {var1’ = eq1, ... } with time-step dt. Here variable(s) ‘var1’, ... are the ones, defined in MGL script previously. The Runge-Kutta 4-th order method is used for solution.





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