19 lines
547 B
Fortran
19 lines
547 B
Fortran
FUNCTION EXPINT(X)
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C ==================
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C
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C First exponential integral function E1(X)
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C
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INCLUDE 'PARAMS.FOR'
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C
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IF(X.LE.1.0) THEN
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EXPINT=-LOG(X)-0.57721566+X*(0.99999193+X*(-0.24991055
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* +X*(0.05519968+X*(-0.00976004+X*0.00107857))))
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ELSE
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EXPINT=EXP(-X)*((0.2677734343+X*(8.6347608925+X*
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* (18.059016973+X*(8.5733287401+X))))/
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* (3.9584969228+X*(21.0996530827+X*
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* (25.6329561486+X*(9.5733223454+X)))))/X
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END IF
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RETURN
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END
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