LET

        [SIC\]LET Variable = Expression [/NEW Type [Attr]]
        [SIC\]LET Variable = Expression /WHERE Conditionmask
        [SIC\]LET Variable [= Expression] /PROMPT "Explanatory text"
        [SIC\]LET Variable [= Expression] /RANGE Min Max
        [SIC\]LET  Variable  [=  Expression]  /CHOICE  Value_1  Value_2  ...
    Value_n
        [SIC\]LET Variable [= Expression] /INDEX Value_1 Value_2 ... Value_n
        [SIC\]LET Variable [= Expression] /FILE Filter


    Assigns a value to a variable. The variable must already be defined (see
    DEFINE)  unless  the  /NEW  option is present. In this case, Type is the
    type of the variable (REAL, INTEGER, DOUBLE  for  double  precision,  or
    LOGICAL).  Logical  expression results cannot be assigned to non logical
    variables, and vice versa. All numerical expression evaluations are done
    in  double  precision,  and  automatically  converted  to  the  type  of
    (numerical) variable assigned.

    The Attr argument is used to specify whether the newly created  variable
    is  LOCAL  (default) or GLOBAL. If no value is assigned to the Variable,
    the user will be prompted for the variable value.

    VECTOR OPERATION:

    Operations are vectorial, i.e. a full array  is  computed  at  the  same
    time.  The variable name can define a subset of an known array, such as:
        DEFINE REAL A[4,5,6] B[4]
        LET A[,,3]  = 1.0  ! or equivalently  LET A[3] = 1.0
        LET A[,2,2] = B    ! or equivalently  LET A[2,2] = B
    these commands assign the value 1.0 to A[i,j,3], with i running  from  1
    to 4 and j from 1 to 5, and B[k] to A[k,2,2] for k from 1 to 4. Implicit
    transposition is now allowed, though still somewhat  experimental:  both
    A[,2,3]  and  A[2,,3]  are  valid.  A  range of indexes can be specified
    rather than one index: for the above example A[3:5]  is  a  valid  4x5x3
    array, A[2:4,,] is a 3x5x6 array.

    IMPLICIT LOOPS:

    In addition to vector computing, it is possible to assign an array using
    "implicit loops", i.e. functions of the array indices such as
        DEFINE REAL A[4,5]
        LET A[I,J] = (I-J)**2
    Implicit loops cannot be mixed with variable index values.

    CONDITION MASK (/WHERE option):

    Vector assignment can be done only where a specified logical  array  (or
    logical array expression) is true, using the /WHERE option. See HELP LET
    /WHERE.

    FREE SYNTAX:

    The LET command may be omitted if no option is present, and is  the  SIC
    syntax is set to FREE. In case of conflict between a variable name and a
    (complete) command name, an error message is issued. See SIC command.

    GUI (Graphic-User-Interface) input mode:

    If command GUI\PANEL has been issued before,  the  LET  command  defines
    widgets  in  the  master  window  defined  by GUI\PANEL. The widget is a
    simple prompt when option /PROMPT is set, a slider if option  /RANGE  is
    present,  a  list of choices if option /CHOICE or /INDEX is given, and a
    selection of files with  the  specified  filter  when  option  /FILE  is
    specified.   If  neither  of  these  options is present, the LET command
    works in the usual way.

    The widgets are created and activated by command XGO. Standard input can
    be  used,  and  pressing  button  GO  will  define  all the variables as
    specified. If button ABORT is pressed instead, none of the variables are
    modified and an error is returned. Error handling is available.