# A Tcl expression consists of a combination of operands, operators, and
# parentheses. White space may be used between the operands and operators and
# parentheses; it is ignored by the expression's instructions. Where possible,
# operands are interpreted as integer values. Integer values may be specified
# in decimal (the normal case), in octal (if the first character of the operand
# is 0 ), or in hexadecimal (if the first two characters of the operand are
# 0x). If an operand does not have one of the integer formats given above, then
# it is treated as a floating-point number if that is possible.  Floating-point
# numbers may be specified in any of the ways accepted by an ANSI-compliant C
# compiler (except that the f, F, l, and L suffixes will not be permitted in
# most installations).  For example, all of the following are valid
# floating-point numbers: 2.1, 3., 6e4, 7.91e+16. If no numeric interpretation
# is possible, then an operand is left as a string (and only a limited set of
# operators may be applied to it).

set a 10
# A Tcl expression consists of a combination of operands, operators, and
# parentheses. White space may be used between the operands and operators and
# parentheses; it is ignored by the expression's instructions. Where possible,
# operands are interpreted as integer values. Integer values may be specified
# in decimal (the normal case), in octal (if the first character of the operand
# is 0 ), or in hexadecimal (if the first two characters of the operand are
# 0x). If an operand does not have one of the integer formats given above, then
# it is treated as a floating-point number if that is possible.  Floating-point
# numbers may be specified in any of the ways accepted by an ANSI-compliant C
# compiler (except that the f, F, l, and L suffixes will not be permitted in
# most installations).  For example, all of the following are valid
# floating-point numbers: 2.1, 3., 6e4, 7.91e+16. If no numeric interpretation
# is possible, then an operand is left as a string (and only a limited set of
# operators may be applied to it).

set b 20
# A Tcl expression consists of a combination of operands, operators, and
# parentheses. White space may be used between the operands and operators and
# parentheses; it is ignored by the expression's instructions. Where possible,
# operands are interpreted as integer values. Integer values may be specified
# in decimal (the normal case), in octal (if the first character of the operand
# is 0 ), or in hexadecimal (if the first two characters of the operand are
# 0x). If an operand does not have one of the integer formats given above, then
# it is treated as a floating-point number if that is possible.  Floating-point
# numbers may be specified in any of the ways accepted by an ANSI-compliant C
# compiler (except that the f, F, l, and L suffixes will not be permitted in
# most installations).  For example, all of the following are valid
# floating-point numbers: 2.1, 3., 6e4, 7.91e+16. If no numeric interpretation
# is possible, then an operand is left as a string (and only a limited set of
# operators may be applied to it).

set c 30
# A Tcl expression consists of a combination of operands, operators, and
# parentheses. White space may be used between the operands and operators and
# parentheses; it is ignored by the expression's instructions. Where possible,
# operands are interpreted as integer values. Integer values may be specified
# in decimal (the normal case), in octal (if the first character of the operand
# is 0 ), or in hexadecimal (if the first two characters of the operand are
# 0x). If an operand does not have one of the integer formats given above, then
# it is treated as a floating-point number if that is possible.  Floating-point
# numbers may be specified in any of the ways accepted by an ANSI-compliant C
# compiler (except that the f, F, l, and L suffixes will not be permitted in
# most installations).  For example, all of the following are valid
# floating-point numbers: 2.1, 3., 6e4, 7.91e+16. If no numeric interpretation
# is possible, then an operand is left as a string (and only a limited set of
# operators may be applied to it).

set d [expr {$a + $b + $c}]
# A Tcl expression consists of a combination of operands, operators, and
# parentheses. White space may be used between the operands and operators and
# parentheses; it is ignored by the expression's instructions. Where possible,
# operands are interpreted as integer values. Integer values may be specified
# in decimal (the normal case), in octal (if the first character of the operand
# is 0 ), or in hexadecimal (if the first two characters of the operand are
# 0x). If an operand does not have one of the integer formats given above, then
# it is treated as a floating-point number if that is possible.  Floating-point
# numbers may be specified in any of the ways accepted by an ANSI-compliant C
# compiler (except that the f, F, l, and L suffixes will not be permitted in
# most installations).  For example, all of the following are valid
# floating-point numbers: 2.1, 3., 6e4, 7.91e+16. If no numeric interpretation
# is possible, then an operand is left as a string (and only a limited set of
# operators may be applied to it).
